Komplexe Halogenidometallate der Gruppe 15 - Struktur, Eigenschaften und neue Funktionalität

In this doctoral thesis I investigated the synthesis of new halogenidometalates of the elements antimony and bismuth. In addition to the basic research of the compound class in terms of structural diversity and synthetic methods, I tried to elucidate the factors influencing the optoelectronic properties. Furthermore, I developed a concept to make halogenidoantimonates and -bismuthates accessible as 2D-materials. The investigations were divided into two subprojects. In the first subproject, the influence of transition metal cations on the optoelectronic properties of halogenido antimonates was investigated. Since only a few ternary compounds were known at the beginning of the investigations, a further aim was to produce additional members of the substance class. For these investigations large organic cations were chosen, whose positive charge is well shielded by sterically demanding organic residues. In this way, the compounds of the publications discussed in sections 3.1 to 3.4 could be obtained by reactions in organic solvents. The reaction of antimony triiodide and copper-(I)-iodide in acetonitrile did not yield a ternary compound of the type [Cu(MeCN)4]2[E2Cu2I10] as observed by Chen for E = Bi, but four transient iodidoantimonates, each of them with a new anion motif. The results show that the binary metalates have not been exhaustively investigated and underline the importance of the crystallization time for the formation of different species. With the addition of phosphonium salts, a number of new compounds could be obtained, including the first iodidoantimonate and the first bromidobismuthate with a ternary anion. I was able to show that the introduction of cuprate units in iodidobismutates results in a change of the absoption properties. A red shift of the onset of absorption is observed. These results are also found for the lighter bromidobismuthates. However, if bismuth triiodide is replaced by antimony triiodide in the synthesis, no redshift of the absorption properties can be observed. Syntheses with metals of the platinum group were also carried out. However, these only resulted in the crystallization of binary palladates and platinates. By dissolving bismuth triiodide and dimethylammonium iodide in acetone an iodidobismutate with a rare new anion with a layered structure could be obtained. This resulted from an in-situ condensation of the ammonium cation with the solvent acetone, forming iminium cations. The cations arrange themselves between the inorganic layers, with very short iodine−iodine interactions between the layers under 4 Å. Quantum chemical calculations have shown that these short iodine−iodine distances lead to a red shift in the absorption properties and thus to an unusually low band gap of 1.87 eV. The compound sublimates at 260 °C and is stable against water and oxygen. The combination of these properties provides the basis for a potential application as a new semiconductor material. In the second subproject I investigated the suitability of halogenido penetelates as new 2D materials. To enable an application in semiconductor technology it is necessary to obtain the compounds as thin films or exfoliable nanosheets. Classical 2D-materials like graphite show layered structures with covalent bonds in one plane. Such structural motifs are, as mentioned above, only rarely found in halogenido penetelates. In order to obtain exfoliable materials nevertheless, I have developed a synthesis route which allows the synthesis of exfoliable halogenido pentelates without covalently bonded layered structure. Various benzylamine derivatives were used for this purpose. By reaction in hydrohalic acids insitu benzylammonium cations are formed, which are arranged along a plane due to their amphiphilic character. Here, the polar ammonium head groups arrange themselves in the direction of the inorganic anions, which are usually mono- or binuclear, and also force them to arrange themselves along this plane. Charge-neutral layers are obtained, which can be split due to the weak Van-der-Waals interactions. Successful exfoliation experiments on a chlorido bismuthate, [BzA]3[BiCl5]Cl, showed that the compound is cleavable despite the lack of covalent interactions within the layers and confirmed the suitability of the compound class as a 2D material. Based on these results, I modified the reaction system to introduce additional functionality into the hybrid compounds. For this purpose a number of chiral amines were tested, of which (R)-(1)-(4-F)PEA proved to be particularly suitable. The obtained halogenido penetelates can also be cleaved along a plane, show absorption edges between 3.35 eV and 2.09 eV depending on the element combination and, induced by the chiral cation, frequency doubling. Combined with a good stability, they are interesting for an application in nonlinear optics.